x86/fpu: Improve FPU detection kernel messages

Standardize the various boot time messages printed during FPU detection:

 - Use a common 'x86/fpu: ' prefix for consistency and to make it easy
   to grep boot logs for FPU related messages

 - Correct speling errors

 - Add printout for the legacy FPU case as well

 - Clarify messages

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>